DC magnetic field sensor based on electric driving and magnetic tuning in piezoelectric/magnetostrictive bilayer

A dc magnetic field sensor possessing an interestingly high electric voltage-driven, magnetic field-tuned dc magnetoelectric (ME) effect is developed based on a bilayer of Pb(Zr, Ti)O₃ piezoelectric transformer and Tb_0.3Dy_0.7Fe_1.92 magnetostrictive substrate. The dc ME effect in the sensor, as evaluated experimentally and theoretically, is induced by driving the bilayer at its zero-field longitudinal resonance frequency (fr0) using an ac electric voltage (Vac) referenced at the input of the piezoelectric transformer, as well as, by tuning the field-dependent compliance and resonance characteristics of the bilayer with the dc magnetic field to be measured (Hdc) upon the negative-ΔE effect intrinsic in the magnetostrictive substrate. The sensor shows a good linear negative response of ac ME voltage (VME) at the output of the piezoelectric transformer to a broad range of Hdc of 0-350 Oe under a small Vac of 2.5 V peak at the designated fr0 of 125.3 kHz. This gives a high negative dc magnetic field sensitivity (S) of -1.58 mV/Oe.